1. Field of the Invention
The present invention relates to a power converter for converting DC current supplied from a DC power source to AC current, and particularly to a layout structure of the power converter.
2. Description of Related Art
Recently, a power converter for converting DC current of a DC power source to AC current and providing the DC current to loads such as a motor as a driving source, etc. is mounted in a vehicle such as a train, an automobile or the like. FIG. 9 shows an example of a conventional power converter 100. The power converter 100 has a switching element which can perform switching of large current, and a switching power module 110 which has a driving circuit for driving the switching element, etc. and is constructed in a box-shape so as to be mounted on a heat sink 112.
Furthermore, the power converter 100 has a smoothing capacitor module 114 for suppressing voltage variation of the DC power source at the switching time to smooth surge of the voltage, and the smoothing capacitor module 114 is mounted on the heat sink 112 so that the smoothing capacitor module 114 and the switching power module 110 are disposed side by side (for example, see JP-A-2004-104860).
The smoothing capacitor module 114 is not necessarily required to be cooled, but it is sufficient to cool the switching power module 110. Therefore, the heat sink 112 may be designed to have an area which is the same level as the switching power module 110. However, in the conventional construction, the mount face (space) of the heat sink 112 must be designed to be larger by the amount corresponding to the mount space for the smoothing capacitor module 114. Therefore, the power converter 100 has been designed to be puffed up in each of weight, cost, volume and height dimension.
Accordingly, there has been hitherto proposed a power converter in which the area of the mount face of the heat sink 112 is reduced by stacking the smoothing capacitor module 114 on the switching power module 110 (for example, see JP-A-2009-111435).
However, when the smoothing capacitor module 114 is stacked on the switching power module 110, the height dimension is designed to be large in scale. Furthermore, the distance L from the smoothing capacitor module 114 to the switching power module 110 is longer, and thus the inductance is increased. Accordingly, a surge voltage occurring at the switching time of the switching power module 110 is increased, which causes breaking of the switching power module 110.